SOLO 35 and 40.
solo 35 vtwin from solo flight limited.solo35 by Solo Flight Ltd

The Solo 35 is a V Twin, overhead valve, air/oil cooled 4 stroke engine. It is a powerful yet light weight and compact engine, which is very economical in terms of both the initial purchase and the running costs. The engine comes complete with electric start, ignition and bat charge circuit, exhaust and prop reduction unit. We can also supply the helix prop specifically designed for this engine.
The Solo 40 is the same engine has above but with further improvements to the cylinder heads and valve gear to give an increase in performance to 40hp.

SOLO 35.                                                                                  View user manual.

Capacity                      650cc
Output                          35hp @ 4200rpm
Max rpm                      4200rpm
Fuel Consumption       4.5 liters per hour at cruise.
Weight                          30kg dry.
only 4100 plus vat and delivery.      

SOLO 40.                                                    View user manual.

Capacity                      650cc
Output                          40hp @ 4400rpm
Max rpm                      4400rpm
Fuel Consumption       5 liters per hour at cruise.
Weight                          30kg dry.
only 4500 plus vat and delivery.     

 With a specification and price like this why would you want to buy a 2 stroke engine?